The present invention relates to a tool for use in dentistry.
Air abrasive cutting is currently in regular use in dental practice and is an extremely useful technique in modern adhesive dentistry where resurfacing and filling materials adhere to the tooth rather than the material, such as amalgams that are keyed for retention. This means that decay can be removed by a process, such as air abrasion, which will remove the decay without the need to cut sound tooth material in order to achieve retention. The surface prepared with the gas abrasive technique leaves a surface ideal for the new materials to bond to. Another advantage of the gas abrasive technique is low stress cutting of the tooth avoiding the stress fracturing found when using conventional rotary instruments. The system also benefits from almost zero heat generation in the cutting process and reduces the need for injections. However the process is slow unless high pressure in the gas or lower pressure and high levels of abrasive media are used. High pressure up to ten bar in some instruments means that the instruments can be difficult to control when cutting teeth, which by nature vary from patient to patient in hardness. There is a relationship between the pain factor and the pressure factor. The higher the pressure, the greater the sensitivity. Increasing the rate of abrasive to air to maintain high cutting rate means that one has a higher than desirable dust debris problem requiring very effective recovery equipment, like powerful aspirators and even external evacuation for airborne particles escaping the oral cavity. Many attachments have been developed in an attempt to eliminate this drawback of gas abrasion devices. These take the form of flexible plastic membrane mouldings that encompass the tip and create a containment area against the tooth surface. These are often connected to aspiration tubes in an attempt to remove the cutting media from the mouth and the cutting face. The problem with these devices is that they encompass the area being cut or polished and observation for the operator is through the device or by lifting away for inspection of the area under treatment. These devices become quickly obscured by the very nature of the materials they are controlling. The invention is based on the realisation that the problem of dust control may be achieved by surrounding the gas stream with a curtain of liquid, conveniently water. Further, the invention is based on the realisation that by forming the curtain in a defined way many benefits result.
In one aspect the invention provides a dental tool comprising a body having a nozzle for providing a stream of pressurised gas containing abrasive media towards a tooth surface, a cap member extending forwardly of the outlet end of the nozzle, the cap member having a bore in generally axial alignment with the bore of the nozzle, the cap having a liquid supply pipe opening into the bore rearwardly of the nozzle outlet, the wall of the bore forwardly of the nozzle being shaped so that liquid emerging from the outlet is caused by the gas stream to form a wall of liquid about the gas stream moving towards the tooth surface.
In another aspect the invention provides a method of treating a tooth, the method comprising drawing a stream of pressurised gas towards the tooth surface, the gas containing abrasive media, the method including the step of drawing a liquid to join the gas stream and shaping the liquid to form a wall about the gas stream.
In yet another aspect there is provided a dental tool comprising a tube having a tapered leading end forming a nozzle of a predetermined diameter, the tube being arranged to supply pressurised gas containing abrasive media to the nozzle, and a cap therefor, the cap having a body of substantially the same shape and a nozzle having a diameter of substantially the same order, a liquid supply tube connected to the cap and having an outlet at a location rearward of the nozzle.
In the invention the liquid is unpressurised and is drawn by the flow of pressurised gas to form a wall about the gas stream. That wall acts as a shielding curtain and has several beneficial effects, as explained in better detail below. While we do not wish the monopoly to be restricted in any way by the following theory, our investigations suggest that the unpressurised drawn liquid is subjected to a Venturi effect to form the curtain.
In yet another aspect the invention provides a dental tool comprising a body having means at one end for performing a dental treatment, and a liquid supply pipeline arranged to supply liquid to the one end, wherein a hand controlled pinch valve is mounted on the tool to control the supply of liquid to the one end.
In yet another aspect the invention provides a dental tool comprising a body having means at one end for performing a dental treatment, the means being at the end of an extension of the body, the extension being rotatable relative to the body.
Other features of the invention are set out in the subclaims.